1. Field of the Invention
This invention relates to a switchgear cabinet including a smoke indicator, which has an intake pipe and, in a housing, a smoke sensor as well as a ventilator or fan, which is disposed downstream of the sensor in the flow path and draws air from an interior of the switchgear cabinet into the housing via an inlet aperture in a housing wall and discharges it via an outlet into the space outside the housing.
2. Description of Related Art
A switchgear cabinet is taught by German Patent Reference DE 198 07 804 A1. In this known switchgear cabinet, which has a closed-off interior, there is an early fire detector including a ventilator of fan, which is disposed externally of the actual switchgear cabinet in an additional cabinet placed on the switchgear cabinet, and early fire detecting sensors, which are disposed in front and relatively close. A supply pipe with a plurality of bores distributed over the length is disposed in the interior of the switchgear cabinet. The supply pipe is connected to a connecting piece protruding from the switchgear cabinet, via which fresh air flows into the interior of the switchgear cabinet when the ventilator is operating. The air passing into the interior flows through this and at the upper side of the switchgear cabinet, is drawn through an aperture located there by the ventilator, which is situated in the additional cabinet. The air drawn out of the entire interior, which air is mixed with the fresh air, flows over the early fire detecting sensors so that a fire is recognized by the sensors.
One object of this invention is to provide a switchgear cabinet of the type mentioned above but where smoke generated as heat develops and can be recognized as early as possible and which responds in a sufficiently sensitive manner even if the switchgear cabinet is partially open.
This object is achieved with the characteristics of an invention as described in the claims and this specification. An intake pipe communicates by its upper end region with the inlet aperture and the housing, which is enclosed in a sealing manner apart from the intake opening and the outlet, and is disposed in the interior of the switchgear cabinet.
Thus, the air to be monitored in the interior of the switchgear cabinet is supplied to the smoke sensor in a targeted manner corresponding to the arrangement and configuration of the inlet apertures of the intake pipe, in such a manner that the smoke sensor responds sensitively to a development of smoke. The smoke indicator is easily installed or respectively fitted as an individual unit in the interior of the switchgear cabinet. The intake pipe can be provided in the interior in a convenient manner, for example with consideration to existing components, with various inlet apertures and, can be assembled, for example, piece-by-piece through plug-in connections.
In an arrangement, which is favorable to the functioning, the housing is disposed in the upper region in the interior of the switchgear cabinet at a spacing from a switchgear cabinet covering wall.
For advantageous, space-saving arrangement possibilities, the housing is mounted on a side wall or door of the switchgear cabinet.
In an advantageous design of the smoke indicator, particularly for production, for assembly and function the intake pipe communicates with a lower housing wall, the ventilator is mounted on an upper housing wall in the region of the outlet, and the smoke sensor is mounted on a base plate of the housing, which base plate connects the lower housing wall and the upper housing wall.
Simultaneously, in a development favorable to the manufacture, installation and maintenance, the lower housing wall and the upper housing wall are formed by portions, bent at right angles to the base plate. A lower housing portion, thus formed for formation of the rectangular housing is closed off with an upper housing portion, which has a U-shaped cross-section. On the covering wall of the upper housing portion, which wall is situated opposite the base plate, both lateral walls are formed by portions which are bent at right angles, and which project up to into the vicinity of the base plate and are detachably connected to the base plate via lateral mounting webs or mounting straps.
If the intake pipe, which is open or closed at its end remote from the intake opening, has air inlet apertures over its length, the interior of the switchgear cabinet can be monitored substantially over its entire height in an even manner or through the corresponding selection of hole distribution per unit length or hole size of the air inlet apertures. For example, certain components are to be especially monitored, weighted with regard to the creation of smoke.
In one design, at least the one door and/or at least one side wall and/or the rear wall of the switchgear cabinet has narrow openings distributed over at least a portion of its surface. The air inlet apertures are disposed on the side of the intake pipe remote from the adjacent door, rear wall or side wall, which provides relatively reliable smoke monitoring of the interior of the switchgear cabinet even in the case of, for example, a switchgear cabinet having a hole pattern or slot pattern in the door or exterior wall.
In a simple, unhindered installation, the housing is mounted on the door.
In a further advantageous embodiment of the smoke indicator with regard to the signal evaluation and control and consequently the function, electrical connecting members for the ventilator and the smoke sensor are disposed in the housing. The smoke sensor and/or the ventilator is connected to a superposed switchgear cabinet monitoring means, which is disposed externally of the housing, with which monitoring means supplied sensor signals and/or ventilator monitoring signals and/or ventilator control signals are receivable, processable or transmittable. Thus, in one embodiment, the smoke indicator is configured so that the smoke sensor, when detecting smoke, switches off the ventilator by a switching-off arrangement provided in the housing. The switching off of the ventilator is determined by the switchgear cabinet monitoring means and data is transmittable to a display device. A separate connection for passing on the sensor signals to the switchgear cabinet monitoring means is superfluous here. The speed monitoring of the ventilator and/or monitoring signal from the switching device can be used, for example, for monitoring the smoke sensor.